1. Field of the Invention
The present invention relates to a liquid crystal display (“LCD”) panel and a method of fabricating the same, and more particularly, to an LCD panel in which a column spacer is applied to a color filter on array (“COA”) structure and a method of fabricating the same.
2. Description of the Related Art
In a general liquid crystal display (“LCD”), an LCD panel comprises a thin film transistor (“TFT”) substrate, a color filter substrate, and a liquid crystal layer sandwiched between the TFT substrate and the color filter substrate. Because the TFT LCD does not emit light on its own, a backlight unit is additionally provided behind the TFT substrate for that purpose. Further, the amount of light transmitted from the backlight unit through the TFT LCD is adjusted depending on the molecular arrangement of the liquid crystal layer.
In fabricating the LCD panel, it is important to precisely align the TFT substrate and the color filter substrate when they are combined to each other. To reduce production costs and to increase the sizes of LCD panels, the sizes of the TFT substrate and the color filter substrate are correspondingly increasing. However, as the sizes of the TFT substrate and the color filter substrate increase, errors in the alignment between the two substrates during their combination are also likely to increase. Thus, problems arise in that defects of the combination increase and the misalignment of the two substrates causes the aperture ratio to decrease.
To solve these problems, a color filter on array (“COA”) structure has been proposed. The proposed COA is composed of a first substrate made by forming a TFT on a TFT substrate material and then forming a color filter layer thereon, and a second substrate facing the first substrate is made by forming a common electrode and a black matrix on a second substrate material or alternatively forming only the common electrode on the second substrate material. The COA structure does not require an additional area for combining the two substrates to each other, thereby decreasing the chances misalignment when both substrates are combined.
In an LCD panel having the COA structure, a spacer is used to maintain a constant cell gap between the first substrate formed with the color filter layer and the second substrate disposed in parallel with the first substrate. Conventionally, a bead spacer has been used as the spacer, but the beads are not irregularly arranged, and as a consequence, a blemish or light leakage arises. To overcome these shortcomings, a column spacer is widely used for maintaining a constant cell gap. The column spacer is regularly arranged on either of the first or second substrates.
When the number of column spacers used is relatively small they may be deformed by pressure, so that the amount of liquid crystal filled between the two substrates is easily controlled. When the amount of liquid crystal is easily controlled, the liquid crystal injection margin of the corresponding display is advantageously increased. However, when only a few column spacers are utilized, stress applied to each individual column spacer are more intense, so that the column spacer may be severely deformed or the column spacer or a film under the column spacer may break.
However, when the number of column spacers used is relatively large, the stress applied to each individual column spacer decreases, but the pressure deformation also decreases, thereby decreasing the liquid crystal injection margin. Thus, there is a trade-off relationship between the former and the latter.